Know the nutrients and dangers that they contain
This year, one nitrate test on cornstalks isn’t enough for cattle producers. Nitrate levels can change dramatically from the time a sample is taken and forages such as cornstalks, sorghum-sudangrass, millet and fescue pastures are harvested.
"Nitrate in the plant becomes nitrite in the rumen," says Tim Evans, University of Missouri veterinary toxicologist. "Nitrates absorbed into circulation from the rumen interact with hemoglobin in the blood, leading to methemoglobinemia, which reduces the ability of the blood to transport oxygen throughout the body of the animal."
The best prevention is accurate information, he says, adding that nitrate tests cost about $25. "Cows will most often eat the leafy areas of the stalks, which contain lower nitrate levels, but I don’t have a lot of faith in cows always eating what we expect them to," he says. "Testing is relatively easy to perform and inexpensive."
Symptoms of nitrate/nitrite intoxication include anxiety, lethargy, exercise intolerance, abortion in late gestation and death. Symptoms can appear as soon as one to four hours after eating, with abortions happening three to five days after consumption.
Test that bale. Sampling cornstalk bales is similar to sampling hay bales, but forage probes should be sized appropriately for cornstalks, says Justin Sexten, University of Missouri Extension beef specialist.
Given the brittleness of stalks and husks, he advises cattle producers to use a larger probe (½" to ¾" wide) that is sharp enough to cut through the corn. To prevent stalks or husks from sliding off the probe, cut at a slower speed than for hay bales.
There is a lot of nutrient variability in cornstalk bales, says Rick Rasby, University of Nebraska–Lincoln Extension beef specialist. "Of any residue, cornstalks have the greatest potential as feed for cow–calf operations.
"Test for moisture, protein and energy in the form of total digestible nutrients, and test for nitrates and aflatoxins. Normally, nitrates are not a major concern, but in extreme drought years, it’s best to test," Rasby says.
With high feed costs, farmers might think about grinding cornstalks to use the whole plant. "At that point, you’re not going to let cows select," Rasby says. "The smaller the screen you grind through, the less the cows will sort. I suggest a 3" to 5" screen. When you are feeding the entire residue, a nutrient analysis as well as a nitrate test is really important."